The invention relates to a rod baffle. In another aspect the invention relates to tube bundles. In yet another aspect, the invention relates to heat exchangers, and to a method and apparatus to radially support the tubes in such heat exchangers and to improve shell side fluid flow distribution.
Heat transfer is an important part of any process. As is well known, an indirect transfer of heat from one medium to another is usually accomplished by the use of heat exchangers of which there are many types. For example, there are double pipe, shell and tube, plate heat exchangers and others. Indeed, the art of heat exchanger design has developed to a very high degree; however, there is still room for improvement in a number of areas. For example, in shell and tube heat exchangers, improving tube support, and also improving the flow pattern of shell side fluids.
Plate type baffles have been used in shell and tube heat exchangers for many years. Such baffles provide support for the tubes at least to some degree. The double segmental plate-baffle heat exchanger is well known to those skilled in the art, and although heat exchangers using plate type baffles were a relatively early development in heat exchanger design, such exchangers are still widely used today. In most plate baffled heat exchangers the passages in the plates through which the tubes pass are slightly larger in diameter than the outside diameter of the tubes in order to facilitate construction of the exchanger. As a result vibration of the tubes can and does occur which frequently results in premature tube failure. Also, exchangers utilizing plate baffles suffer from relatively stagnant volumes in the flow of shell side fluid immediately downstream of each baffle, in the sheltered area. Heat transfer is adversely affected. Further, especially where heat exchangers having plate-baffles are utilized for steam generation, localized overheating and vaporization can occur in the stagnant regions, causing scale formation and loss of heat transfer efficiency. Further, scale deposition or crevice corrosion can occur between the baffle and the tube which can lead to tube failure in the bundle.
U.S. Pat. No. 2,693,942, issued to J. R. Guala on Nov. 9, 1954, describes a heat exchanger utilizing plate-baffles arranged so as to provide a helical flow pattern of shell side fluid. A disadvantage of the apparatus disclosed by Guala is that it is extremely difficult to construct. Each baffle comprises two criss cross plates, with each plate being in the form of a segment of an elipse and pierced to permit passage therethrough of the tubes of the bundle. Construction of such a bundle would clearly be quite difficult.